Hydraulic system control



Feb. 23, 1960 R. 1 swlrzER 2,925,718

HYDRAULIC SYSTEM CONTROL Original Filed July 2, 1956 2 Sheets-Sheet 1rn- I Feb. 23, 1960 R, L. SWITZER HYDRAULIC SYSTEM CONTROL Grignal FiledJuly 2, 1956 2 Sheets-Sheet 2 United States Patent O HYDRAULIC SYSTEMCONTROL Robert L. Switzer, Long Beach, Calif., assignor to Union OilCompany of California, Los Angeles, Calif., a corporation of CaliforniaOriginal application July 2, 1956, Serial No. 595,535. Divided and thisapplication July 24, 1958, Serial No. 750,684

7 Claims. (Cl. 60-97) This invention relates to the automatic control ofhydraulic systems for the delivery of power by means of hydrauliccylinders and particularly relates to improvements in the control ofsuch systems whereby the mechanically actuated pilot valves normallyassociated with the hydraulic cylinder in such systems have beeneliminated. The invention also relates to an improved hydraulic cylindermodified to permit automatic hydraulic signalling when the end of theextension and retraction strokes are reached by the piston.

Reciprocal motion of mechanical elements is widely used in mechanicaldevices of all kinds, some of which deliver power in appreciablequantities and others of which are merely used to actuate other elementsat low force levels. Hydraulic cylinders containing a piston and pistonrod are frequently used to generate such reciprocating motion, butheretofore they have required some means for detecting and signallingthe time when the piston reached the end of its stroke in the cylinder.Ordinarily this detection and signalling is by means of a mechanicallyactuated pilot valve placed near the piston rod and tripped by means ofkickers attached to it. The movement of the pilot valve alters the iiowof hydraulic fluid through the valve and ultimately permits the reversalof the fluid ow to and from the cylinder so as to either retract orextend it depending upon which extreme has caused the signal generation.j

Although such pilot valves are generally reliable, they are frequentlydiicult to maintain in some locations, particularly if they aresubmerged in a liquid medium, or located within a closed vessel, or inany other elements inaccessibly located.

One specific example of such inaccessibility lies in the feeder caseenclosing the oscillating-reciprocating feeder mechanism employed in theupiiow oil shale retort. Herein the reciprocating feeder is operated bya hydraulic cylinder which is contained within the feeder case andcompletely submerged therein in a body of shale oil. lt is in general ofadvantage to eliminate the customary mechanical pilot valves in anysituation since it constitutes a moving part of the mechanism which canbe a source of trouble.

The present invention is therefore directed to an improved hydraulicsystem in which some or all such pilot valves are eliminated. Theinvention further relates to an improved hydraulic cylinder modified toprovide self-signalling when the piston reaches either extreme of itsstroke.

It is therefore a primary object of this invention to provide animproved hydraulic system for the generation of a reciprocating motionat any desired power level without the requirement of hydraulic pilotvalves associated with the mechanism.

It is a more specific object of this invention to provide an improvedhydraulic means for operating reciprocating pumps without the use ofpilot valves.

'One specific object of this invention is to provide an improvedautomatic hydraulic system for operating a ice single reciprocatingload, such as an oil well pump, hydraulically without the use of pilotvalves.

Another object of this invention is to provide an improved hydraulicsystem for operating the oscillating and reciprocating solids feeder inthe upow shale retorting process.

It is another `object of this invention to provide an improved hydrauliccylinder modified to provide selfsignalling when the piston reacheseither extreme of the stroke.

It is also an object of this invention to provide an improved apparatuscapable of effecting the foregoing objects.

Other objects and advantages of the present invention will becomeapparent to those skilled in the art as the description and illustrationthereof proceed.

Briefly the present invention comprises an improved hydraulic systemhaving for its essential element a modified hydraulic cylindercontaining a piston and piston rod, provided with the conventional uidinlets and outlets adjacent each end of the cylinder, and modified toprovide pilot fluid inlets in the cylinder wall adjacent each end of thepiston stroke. These pilot uid inlets are located a distance away fromthe end of the cylinder which is less than the thickness of the pistoncontained therein, or less than the span occupied by piston -rings onthe piston side, so that when the piston has moved to either extreme ofthe cylinder, the pilot fluid inlet at that end is sealed either by thepiston or by or between the piston rings, or both, so that no pilotfluid may enter or leave the cylinder through the pilot inlet.

In operation this modied hydraulic cylinder is supplied with hydraulicliuid through the usual inlets and outlets to move the piston in eitherdirection in the conventional way. A pilot iiuid obtained from thehydraulic pump supplying fluid to the cylinder is introduced at a rela:tively low rate into each of the pilot inlets through separate linesandv preferably each of these lines is provided with a check valvepermitting flow into the cylinder only. When the piston is moving fromone extreme to the other, pilot uid will not ordinarily flow into thepilot Huid inlet adjacent the high pressure end of the cylinder becausethe pilot uid pressure will not ordinarily exceed the pressure of themain hydraulic uid stream. The other end of the cylinder is ventingdisplaced iiuid to the hydraulic reservoir a-t a low pressure andtherefore pilot fluid will flow into the pilot inlet near the lowpressure or venting end of the cylinder and flow directly out againthrough the main uid connection as it is displaced by the moving piston.At the end of the stroke however the pilot inlet at that end is sealedby the piston or its rings and accordingly the pilot iiuid pressure inthis inlet rapidly rises signalling the end of the piston stroke. Thispressure increase is the pilot signal obtained from the modifiedhydraulic cylinder of this invention so that no mechanically operatedpilot valve is needed. The signal so obtained can be used to operate themain direction reversing hydraulic valve controlling liow of hydraulicuid to and from the cylinder through the principal or main connectionsso as to reverse the principal fluid ow and cause the piston to move inthe reverse direction. At the end of this reverse stroke, the otherpilot inlet is sealed in the same manner, and a pressure rise isgenerated in that pilot uid inlet. This signal indicates the other endof the stroke and causes the direction reversing hydraulic valve to bemoved back into the original position completing the hydraulic cycle.

The present invention is most readily understood by reference to theaccompanying drawings in which:

Figure 1 shows a schematic piping and instrumentation diagram of ahydraulic system using a single hydraulic cylinder operated in atwo-step sequence, and

n Figure 2 shows a schematic piping and instrumentation dlagram ofhydraulic system utilizing two .hydraulic cylinders operated in afour-step sequence to oscillate and reciprocate one of the cylinderSystem, Fig. 1 modification Referring now particularly to Figure 1,hydraulic cylinder provided with piston 12 and having piston rings 14 ismounted by means of supports 16 and connected to a suitablereciprocating load, not shown but which may to a load such as a bottomhole oil well pump, by means of piston rod 18. Cylinder 10 is providedwith the conventional main connections 18 and 20 for hydraulic fluid.Also provided according to this invention are pilot fluid connections orinlets 22 and y24 opening through the wall of hydraulic cylinder 10 adistance from each end thereof which is less than the thickness ofpiston 12, or the span of piston rings 14. This distance is determinedso that with piston 12 in the position shown, pilot inlet 22 is sealedagainst fluid introduction by the piston or its rings. Similarly pilotHuid inlet 24 is sealed when piston 12 is at the top of the stroke inFigure 1. Hydraulic fluid from oil reservoir 26 flows through outletline 28 into oil pump 30. Oil is pumped therefrom through check valve 32and on through rrate control valve 34 into a four-way directionalcontrol valve DCV having port, P, T, 1 and 2. The high pressure oilopens thereinto lthrough port P. Directional control valve DCV isconnected from port 1 by means of line 36 to upper main hydraulic oilconnection 18 and lower main Iconnection 20 communicates through line 38to port 2 of DCV. The Vented hydraulic oil displaced `from cylinder 10,is removed from port T of DCV, ows through line 40 provided with check.valve 42, and continues back to reservoir 26 through lter and cooler 44.With directional control valve DCV in* .the position shown, highpressure oil is supplied through line 36 to the top of cylinder 10moving piston 12 downwardly therein, While displaced oil is ventedthrough lines v38 and 40 back to reservoir 26. With DCV moved to theleft, the hydraulic oil passes through DCV between ports P and 2, isintroduced to the bottom connection of cylinder 10 causing piston 12 torise, and the displaced hydraulic oil passes through line 36 and throughDCV between ports 1 and T back to reservoir 26.

Directional control valve DCV thus selects the main `hydraulic oilconnection of cylinder 10 to which the high .pressure oil is suppliedand thus determines the direction -of movement of piston 12. DCV isactuated and moved `from left to right between the two exteremepositions Iby means of hydraulic operators 46 and 48. These -operatorsare in turn actuated by a pilot pressure impulse from either of controlvalves CV-l or CV-2. Control valve CV-l in turn is actuated by hydraulicoperators 50 'and 52 while -control valve CV-Z is actuated by hydraulicoperators 54 and 56. Control Valves CV-l and CV-Z are Spring loaded bymeans of springs 58 and 60 biasing them into the positions shown wherebyDCV operators 46 and 48 are vented into reservoir 26. -Each of controlvalves CV-1 and CV2 controls the tlow of pilot iluid to the hydraulicoperators 46 and 48 to actuate directional control valve DCV in responseto the signal pressure increase in the pilot fluid connections. Thesignal pressure rise actuates control valves CV-1 and CV-2 through theirhydraulic operators against loading springs 58 and 60. Ports 2 of eachof CV-l and CV-2 are blocked so that these valves are in realitythree-way control valves. Port 1 of CV-l is connected through line 70 tohydraulic operator 4S and port'l of CV-2 is connected through line 72 tohydraulic operator 46, .both of which operators actuate directionalcontrol valve DCV. A supply of pilot uid is taken from point 62 on themain high pressure hydraulic oil line, and is counected by means ofpilot oil manifold 64 and line 66 to port P of CV-l and line 68 to portP of CV-Z. These ports are normally closed because of loading springs 58and 60. Ports T of each of CV-1 and CV-2 are conneoted through pilot oilvent manifold 70 to reservoir 26.

Hydraulic operator S0 of CV-l is connected through line 74 and line 38to lower main hydraulic connection 20 of cylinder 10. Hydraulic operator54 of CV-2 is connected through line 76 and line 36 to upper mainhydraulic connection 18 of cylinder 10. Thus when a high pressure existsin either of the main connections 18 or 20, as when the high pressureoil is applied therethrough to move piston 12 in one direction or theother, it is reflected through lines 36 and '76 or lines 38 and 74 sothat hydraulic operators 54 and 50 respectively, in conjunction withloading springs 58 and 60, force control valves CV-l or CV-2 to theright into the positions shown. The loading springs are required toprevent the main high pressure fluid from backing up through pilot lines78 and 80 and actuating operators 52 and 56 thereby moving CV-l and CV-2in the reverse direction.

The supply of pilot fluid injected directly at pilot inlets 22 and 24near the ends of cylinder 10 is obtained from the main hydraulic lines36 and 38 referred to previously. Lower inlet 22 receives pilot fluidthrough line 78 provided with control valve 81 and check valve 83 and italso connects to and actuates hydraulic operator 52. Upper pilot iluidinlet 24 receives oil from main hydraulic line 38 through line S0provided with control valve 85 and check valve 84 and is also connectedwith hydraulic operator 56. With this connection a high pressure atlower pilot inlet 22 signalling the arrival of piston 12 at the bottomof hydraulic cylinder 10 actuates hydraulic operator 52 moving CV-l tothe left against loading spring 58 and thereby supplies pilot hydraulicfluid to hydraulic operator 48 moving DCV to the left. Similarly thearrival of piston 12 at the top of the stroke seals pilot inlet 24,causes the pressure in line to rise, actuates hydraulic operator 56moving CV-Z to the left against loading spring 60, and thereby suppliespilot iluid pressure through line 72 to actuate hydraulic operator 46moving DCV back to the right in the position shown. In this Way themovements of piston 12 in hydraulic Icylinder 10 signal the arrival ofthe piston at the extremes of piston travel and causes a reversal of themain flow of hydraulic fluid so as to return the piston toward theopposite extreme. The system continues in this reciproeating motionindefinitely at a rate controlled by valve 34 and pump 30 which regulatethe rate at which high pressure hydraulic fluid is supplied tol cylinder10 to move piston 12.

peration, Fig. 1 modification A complete descrip-tion of the movementsequence of each of the three valves DCV, CV-l, and CV-Z, and thereciprocation of piston 12 in hydraulic cylinder 10 is given immediatelybelow to provide a concise and clear description of the operation ofthis modication of the apparatus of this invention. In Figure 1 piston12 is shown arriving at the bottom of its downstroke. During thedownstroke the weight of the load, if any, plus the weight of piston rod18 and piston 12, plus the supply of high pressure tluid through line 36to upper inlet 18 of the cylinder causes piston 12 to move downwardlythrough cylinder 10. During this time a small ilow of pilot uid into thelower pilot uid inlet 22 is maintained from line 36 through pilot line78. Meanwhile displaced luid ows through lower main hydraulic connectiontogether with the ypilot fluid -which is introduced through inlet 22 andflows through line 38 and DCV back to reservoir 26.

When lpiston 12 arrives at the lowest position, pilot inlet 2-2 issealed and the pressure there and in line .78 rises suiciently tolactuate operator 52 and move CV-l to the `left against lspring 58, Thisplaces pilot fuid pressure through ports P and 1 of CV-1 onto operatorl48 moving DCV to the left. This connection vents hydraulic uid from thetop of cylinder while supplying high pressure fiuid through lower mainconnection 20 to raise piston 12. Since connection 18 is now vented,this relieves pressure at pilot inlet 24 permitting CV-Z to return toits right-hand position shown through the action of spring 60.

The piston now moves upwardly connected to the load through connectingrod 18. When the piston arrives at the top of the stroke, upper pilotinlet 24 is sealed against further pilot iiuid ow from line 38 throughline 80. The pressure rises and this pressure impulse is transmittedthrough line 80 to operator 56 movin-g CV2 to the left against spring 60thereby placing pilot iiuid pressure therethrough between ports P and 1and through line 72 to operator 46 moving DCV to the right therebyreversing the main flow of hydraulic uid. The bottom of cylinder 10 isnow vented through line 38 and high pressure uid is supplied throughline 36 to return the piston toward the bottom position. This relievesthe high pressure formerly below piston 12 and also at the lower pilotinlet 22 lowering the pressure at operator 52 and permitting CV-l toreturn to the right-hand position shown by means of loading spring 58.

- Piston 12 is now moving downwardly toward the lower position to beginthe cycle all over again. The cycle continues indefinitely at a ratedetermined by the rate of supply and the pressure of the main stream ofhydraulic fluid. The end of each of the two steps is signalled by thepilot pressure increase, and this begins the next step. The weight ofthe piston 12, shaft 18, and the load is prevented from causing thepiston downstroke by check valve 162, valve 164, and back pressurecontroller 166 which maintain during the downstroke a pressure belowpiston 12 which is suflicient to support the weight. A slightly greaterpressure above piston 12 will cause the downward movement.

As stated briey above, the modification shown in Figure l isparticularly adaptable to the hydraulic pumping of oil wells by means ofa hydraulic cylinder having a diameter of from 2 to 12 inches or moreand a stroke of from 2 to 40 feet located at the surface of the earthand connected through a string of sucker rods to a bottom hole pump inthe well. Obviously the apparatus is adapted to any other use in which areciprocal motion in power application is required. This reciprocalmovement can be vertical as described, horizontal, or at any otherangle. These other applications of course will present description.

System, Fig. 2 modification Referring now -more particularly to Figure2, a more complex four-step modification of the present invention isshown using one mechanically actuated pilot valve employing twohydraulic cylinders and is adapted for use in operating the solidsfeeding mechanism of the upflow shale retorting process. In thismodification, a first or main feed cylinder 100, which drives the pistonin a solids feeder, is oscillated between the vertical position shownand an inclined position, not shown, around trunnion 102. Thisoscillation is imparted by means of a second or oscillating cylinder 104provided with piston 106 and piston rod 1108 which is integrallyconnected by any means not shown to cylinder 100. Feed cylinder 100 isprovided with piston 110, piston -rod 112, and the solids feeder notshown at the upper end of the piston rod. Cylinder 100 is inclined fromthe vertical by extending cylinder 104 at a time when piston 110 isextended. Crushed oil shale is supplied to the top of the solids feederpiston and cylinder system, piston 110 is retracted accepting a chargeof shale, feeder cylinder 100 is returned from this charging position tothe vertical feeding position by retractingoscillating piston 10,6, and

The end of each step in the sequence signals the start of the next step.This four-step sequence cycle is continued to force periodic charges ofoil shale upwardly into the retort.

In Figure 2 the piping and instrumentation connections by means of whichthe foregoing sequence of operations is effected are shownschematically. The main hydraulic conduits are shown as solid lineswhile the pilot fluid connections are shown as broken lines. Feedercylinder is provided with upper and lower ends with the usual mainhydraulic fluid connections 114 and 1.16, hydraulic fiuid beingintroduced through 114 and vented through 116 to extend piston 110 andpiston rod 112, and subsequently being introduced through inlet 116 andvented through 114 to retract piston 110 and piston rod 112. Alsoprovided adjacent each end of feeder cylinder 100 are lower and upperpilot tiuid connections 118 and 120. These pilot fluid connections aredisposed a distance from the end of the cylinder which is less than thethickness of piston 110. Piston is providedwith piston rings 122 whichseal, as shown in the drawing, pilot uid connection 118. Pilot fluidconnection is similarly sealed when piston 110 is in its upper orextended position. The function of these connections so placed has beenreferred to above in connection with Figure 1 to provide a pressuresignal indicating the arrival of the piston at the ends of its stroke.This signal is utilized to change the flow of hydraulic fluid in thesystem so as to continue automatically the sequential operation offeeder cylinder 100 and oscillating cylinder 104.

The present system is provided with hydraulic fluid reservoir 124 havingfilling line 126. Outlet line 128 opens into iiuid pump which delivershigh pressure hydraulic uid into manifold 132. This fluid is dividedinto two principal streams, one iiowing through line 134 at a ratecontrolled by valve 136 through four-way rlirection reversing valveDCV-2 to oscillating cylinder 104, and the other through line 138 at arate controlled by valve 140 through four-way direction reversing valveDCV-1 to feeder cylinder 100. Displaced hydraulic fluid is vented fromoscillating cylinder 104 through line 157, back through valve DCV-2 andthrough line 135 into low pressure manifold 137. Displaced low pressurehydraulic iiuid passes from feeder cylinder 100 through valve DCV-1through line 139 through low pressure manifold 137. The returninghydraulic fiuid is passed through a cooler and a filter indicatedgenerally at 141 and returned to reservoir 124. The rate of movement ofpiston 106 in oscillating cylinder 104 is ycontrolled by the setting ofvalve 136. Similarly the rate of movement of piston 110 in feedercylinder 100 is controlled by the setting of valve '140.

Direction reversing valve DCV-2 is actuated by means of hydraulicoperators 142 and 144 and serves to provide high pressure hydraulicfluid to and vent low pressure hydraulic fluid from the fluidconnections at the end of oscillating cylinder 104. Similarly, directionreversing valve DCV-1 is actuated by hydraulic operators 146 and 148 andprovides hydraulic fluid to and vents uid from ticrnections 114 and 1,16at the ends of feeder cylinder Operators 142 and 144 which actuatedirectional control valve DCV-2 are themselves actuated by pilot fluidthrough control valves CV-l and CV-2.

Control valve CV-l is actuated by hydraulic operators 143 and 145, andcontrol valve CV-2 is actuated by operators 150 and 152 by means ofsignal pressures obtained in part from the pilot fluid lines and in partfrom rotary pilot valve RPF. As noted on the drawing, control valves CV1and CV-Z are spring loaded by means of loading springs 147 and 1 49whichtendto ,biasgthem to the assuma left into the positions :shown inwhich both operators 142 and 144 of DGV-2 are vented .to reservoir 124.Thus the impulse generated by operators 143 and 150 must overcome thecompression force of these loading springs in order to move valves CV-land CV-Z to the right. Once the signal pressure is removed fromoperators 143` and 150, the loading springs return then to the positionsshown in the drawing. In the present invention where feeder cylinder 100oscillates about trunnion 102, it is simple to bring an extension rodthrough the feeder case from trun-nion 102 provided with arm 154 andkicker 156 which actuates rotary pilot valve RPV at the extremes of theoscillation. The extremes of reciprocation of piston 110 are diicult tosense however because of the location of this cylinder within a sealedoil filled case. Accordingly the pilothydraulic inlets 120 and 1118 arerespectively used according to the present invention to provide thesignal pressures to actuate operator 150 when piston 110 reaches the topof its stroke and hydraulic operator 143 when piston 110 is in theposition shown at the bottom of its stroke.

Briefly, then, rotary pilot valve RPV signals the extremes in theoscillation of feeder cylinder 100, which actually is the same yassignalling the extremes of reciprocation of oscillating cylinder 104, soas to actuate directional control valve DCV-l through hydraulicoperators 14-6 and 148. Pressure increases in connections 118 and 120signal the arrival of piston 110 at the extremes of travel in feedercylinder 100 so as to operate control valves CV-l and CV-2 which in turnoperate direction reversing valve BCV-2 for the purposes discussedabove.

Direction reversing valve BCV-2 is connected at ports 1 and 2 by meansof lines 155 and 157 to oscillating cylinder 104. Direction reversingvalve DGV-1 is connected at ports 1 and 2 respectively with main iuidconnections 116 and 114 of feeder cylinder 100 by means of lines 158 and160. As will be noted, lthese latter two lines are provided with severalcheck valves and back pressure controllers for the specific purposesdiscussed below.

Line 160 is provided with check valve 162, permitting fluid flow onlytherethrough into connection 114, and control valve 164 actuated by backpressure controller 166 connected in parallel therewith. The purpose ofthis back pressure controller is to maintain during the downstroke ofpiston 110 a predetermined minimum hydraulic pressure below piston 110which prevents the Piston from moving downwardly, because of its ownweight and the weight of the piston rod and the load 'attached thereto,atan undesirably high rate.

Line 158 is provided with check valve 168, permitting outflow ofhydraulic fluid from connection 116 only, and control valve 170connected in parallel therewith and actuated by pressure reducer 172.The purpose of this pressure reducer is to limit the maximum hydraulicpressure which can be placed in cylinder 100 at port 116 above piston110 during the retraction stroke. LThis pressure need not be as great asthe pressure applied to lift piston 110 since the weight of the load,the piston rod 112, and piston 110 act in a direction which aids theretraction of the piston.

Line 158 is further provided with check Ivalve 174, permitting outflowof fluid only from cylinder 100 .above piston 110, and control valve 176connected in parallel therewith and actuated by back pressure controller178i. The purpose of this back pressure controller is to generate a backpressure in line 158 at point 180 during the retraction stroke of piston110 so as to generate a signal pressure through control lines 182 and184 -at pilot fluid inlet 118 when piston 110 reaches its retractedposition, which pressure signal is sufficiently high -so that it Willactuate Ithrough line 186 hydraulic operator 143 against the loadingspring 149 in control valve CV-L Hydraulic pilot uid flow intoconnections 118 and 120 is derived from the high pressure fluid flowdirected through direction reversing valve DCV-l and through lines 158and 160 into main connections 116 and 114.

Thus when high pressure fluid is being introduced through connection 114during the extension stroke of piston 110, a minor portion of the uidflows through line 190 provided with control valve 192 and check val-ve194 through the upper pilot hydraulic connection 120. The pressure risein this line from the vent pressure Ito the supply value generated bythe arrival of piston 110 at the extension end of the stroke istransmitted through line 196 to operato-r 150 which moves control valveCV-2 to the right against loading spring 149. When high pressurehydraulic fluid is being introduced through line 158 to the upper mainconnection 116 in feeder cylinder 100' during the retraction stroke, aminor ow is taken from line 158 at point 180, is passed through line 182provided with .control valve 198 and check valve 200, then through line184 into lower pilot hydraulic inlet 118. The pressure rise from thevent pressure to the supply valve signalling the `arrival of piston 110at the retracted extreme, as shown in the drawing, is detected at point202 and is transmitted through line 186 thereby actuating hydraulicoperator 143 and moves control valve CV-l to the right against loadingspring 147.

As stated above, these aforementioned movements to the right of controlvalves CV-l and CVeZ permit the ow of pilot hydraulic fluid from highpressure manifold 134 through pilot uid manifold 204 provided with valve206 and, respectively, through lines 208 and 212 through control valveCV-l at ports P and 2 through line 214 to actuate operator 144 and moveDGV-2 to the left, and through line 210 through control valve CV-2 atponts P and 2 through line 216 to :actuate operator 142 to move DGV-2 tothe right. The ow of hydraulic fluid to and from oscillating cylinder104 is thus controlled.

High pressure pilot manifold 204 is also connected through line 218 toport P of rotary pilot valve RPV. As stated above, this pilot valve ismechanically actuated by the :oscillation of feeder cylinder 100. Whenthe feeder cylinder reaches the vertical or feeding position shown inthe drawing, a position in which the piston 110 is also in its lower orretracted position, rotary pilot valve RPV is internally connectedbetween ports P and 2 thereby permitting the high pressure hydraulicpilot fluid to flow through line 220 to hydraulic operator 148 movingdirection reversing DCV-l to the left. This permits the ow of highpressure hydraulic fluid through the main line 138 through DGV-1, portsP and 2, on through line 160 to the bottom connection 114 of cylinder100 thereby raising piston 110. At the top of this stroke and aspreviously described, feeder cylinder is oscillated into an inclinedposition which again actuates rotary pilot valve RPV by means of kicker156 so as tto connect ports P and 1. This permits high pressure pilotfluid to ow through RPV, through line 222 to hydraulic operator 146which moves DCV-l into the position shown. This supplies `a main highpressure stream of hydraulic uid through lines 138 and 158 to openconnection 116 to retract piston in feeder cylinder 100.

Ports T on each of rotary pilot valve RPV and control valves CV-l andCV-2 are connected respectively by means of lines 224, 226, and 228 tolow pressure pilot fluid manifold 230 through which it is returned tofluid reservoir 124.

The foregoing discussion briefly describes the functions and theinterconnections between each of the essential elements of the systemdescribed in Figure 2. The operation will be perhaps most readilyunderstood by following the motions of each element through a completecycle of operation. Such a cycle is described immediately below.

Operation, Fig. 2 modification Figure 2 shows the feeder cylinder 100 inits fully re. tracted position and also shows the oscillating cylinder104 in its fully retracted position. Ihe setting of RFV shown,resultingfrom the movement ofcylinder 100 into the vertical position,supplies high pressure pilot uid through ports P and 2 tohydraulic'operator 148 While venting hydraulic operator 146 throughports T and 1 thereby shifting directional control valve DCV-l to theleft. This connects ports P and 2 and connects ports 1 and T in DCV-lthereby directing high pressure uid through line 160 to the bottom ofcylinder 100 causing piston 110 to rise delivering shale into the kiln.The uid lying about piston 110 is vented through connection 116 andthrough line 158, through ports 1 and T of DGV-1, and lines 139 and 137to reservoir 124.

At the same time as high pressure iluid is introduced through inlet 114,a small pilot uid stream passes into upper pilot fluid inlet 120 throughline 190. When piston 110 reaches the fully extended position, thispilot uid flow at inlet 120 is cut oi causing the pressure at 181 inline 190 to rise signalling the end of the feeder cylinder 100 extensionstroke. This places a high signal pressure through line 196 on hydraulicoperator 150 suicient to actuate it against loading spring 149 therebymoving control valve CV-2 to the right. This connects ports P and 2 andports 1 and T of CV-2. High pressure pilot uid is thereby passed throughports P and 2 through line 216 on to hydraulic operator 142 movingdirection reversing valve DGV-2 to the right. This places high pressurehydraulic fluid through line 134, connected ports P and 1 in DGV-2,through line 155 to the lower port of oscillating cylinder 104 causingpiston 106 to move into the extended position thereby oscillating feedercylinder 100 into the inclined charging position while piston rod 112 isextended.

Upon reaching the fully inclined position, kicker 156 again actuates RPVthereby connecting ports P and 1 and connecting ports T and 2. Highpressure pilot lluid ows from line 218 through connected ports P and 1in RPV, through line 222 to actuate hydraulic operator 146 moving DCV-lto the right connecting ports 1 and P and connecting ports 2 and Tthereof. This places high pressure hydraulic uid from pump 130 throughline 158 into upper inlet 116 while venting displaced hydraulic fluidfrom cylinder 100 through lower connection 114, line 160, connectedports 2 and T in DCV-1, back to reservoir 124. While high pressure fluidthus ows through line 158 into upper connection 116, a small highpressure pilot stream flows through lines 182 and 184 into lower pilotuid inlet 118 only so long as piston 110 does not seal this inlet. Whenpiston 110 is fully retracted, in accepting a fresh charge of oil shale,pilot uid inlet 118 is sealed causing pressure to rise at point 202.This actuates through line 186 hydraulic operator 143 moving CV-l to theright against loading spring 147 thereby connecting ports P with 2 andport l with T in CV-l. Pilot hydraulic uid ows from lines 132, 204, 208and 212 through ports P and 1 of CV-1, through line 214 actuatinghydraulic operator 144, moving direction reversing valve DCV-Z to theleft thereby connecting ports P and 2 and ports T and 1 in DGV-2. Highpressure hydraulic lluid then ows through DCV-Z through connected portsP and 2, through line 156 to the upper connection on oscillatingcylinder 104. This causes the piston 106 to retract. Hydraulic fluid isvented from the lower connection in cylinder 104 through line 155 andconnected ports 1 and T in DGV-2, through lines 135 and 137 to reservoir124. This brings oscillating cylinder 104 back into the position shownin Figure 2 thereby oscillating feeder cylinder 100 into the vertical orfeeding position also shown in the drawing. This causes kicker 156 againto trip rotary pilot valve RPV thereby interconnecting ports P and 2 andports T and 1. This begins the cycle all over again. Pilot fluid flowsthrough line 21S and connected ports P and 2 and RPV, then through line220 actuating hydraulic operator 148 moving direction reversing valveDCV-l to the right thereby connecting port P with 2 and port to lowerconnection 114 in feeder cylinder .'100 forcing piston 110 upwardly todeliver the charge of oil shale into the kiln.

The cycle automatically repeats in the aforementioned steps causing acontinuous alternate extension and retraction of each of cylinders and104 in the sequence described.

It is obvious from the foregoing description the manner in which thepilot valves formerly used have been eliminated from the mechanismassociated with piston rod 112 in cylinder 100 and have been substitutedwith lower and upper hydraulic fluid inlets 11S and 120. Rotary pilotvalve RPV was only used because trunnion 102 was readily fitted with asealed shaft which could be brought through a seal in the feeder caseenclosing feeder cylinder 100 and oscillating cylinder 104. It should beunderstood that in other situations it may be inconvenient to use rotarypilot valve RPV and it may be eliminated together with its mechanicalactuation means and oscillating cylinder 104 may be provided with thetwo hydraulic fluid inlets at each end in a manner entirely analogous tothat shown in connection with feeder cylinder 100. In this situation allpilot valves are eliminated and the moving cylinders may be completelyenclosed in inaccessible positions and the signals indicating the end ofeach piston stroke obtained by pressure increases in the hydraulic iluidinlet lines as described in connection with cylinder 100 in Figure 2.

The system shown in Figure l was employed in actuating a bottom holepump in an oil well located in southern California. The well was 7,800feet deep, the actuating cylinder was 30 feet long, and 8 inches indiameter. Hydraulic fluid was applied thereto at a pressure of 500 to800 p.s.i. to move the sucker rod upwardly so as to actuate the pump.The cycle was continued at a rate of approximately 6 strokes per minutewhile pumping at a rate of 400 barrels per day. The system was entirelysuccessful, operated for extended periods without maintenance, and madesubstantially no noise while in operation.

The system of Figure 2 was employed in actuating the so-called rock pumpin the upow shale retorting process. In this modification crushed shalerock was fed to the retort at a rate of about 350 tons per day in aretort which was 17 feet in diameter and about 35 feet high. The shalefeeder cylinder was 66 inches in diameter, had a stroke of 24 inches,and was operated at a rate of l0 strokes per hour by means of thehydraulic system indicated in Figure 2. The oscillating cylinder had astroke of 4 feet and was 16 inches in diameter. The feeder cylinder,which actuated the shale piston feeder, had a stroke of 2 feet and was32 inches in diameter. The hydraulic fluid was supplied in the system ata maximum of 2,000 p.s.i.g., the pilot hydraulic iiuid was used in thesystem at a maximum pressure of about 200 p.s.i.g. by means of valve 206shown in Figure 2, the lower feeder cylinder pressure was maintained bymeans of back pressure controller 164 to a value of about 200 p.s.i.g.during the downstroke, the pressure in the top of feeder cylinder 100was limited by means of pressure controller 172 during the downstroke toa maximum of about 1,000 p.s.i.-g., and back pressure controller 178during this same downstroke maintained a pressure differential of about200 p.s.i.g. across valve 176 so as to supply at point 180 a source ofpilot hydraulic fluid of a suicient pressure during the downstroke togenerate at point 202 when piston is in its fully retracted position ahydraulic pressure suiciently high to actuate hydraulic operator 143 incontrol valve CV-1.

The present invention has been described above by way of illustration inconnection with two processes in which it has been used. The apparatusof Figure 1 and T with 1. This supplies high pressure hydraulic fluid 75Example l is relatively simple employing a single hy.

.draulic cylinder which has been provided at its end'with twooscillating pilot hydraulic fluid inlets for the purposes described. Thesystem of Figure 2 and of Example 2 is more complicated because of itssimultaneous reciprocating and oscillating movements. The princi- '.plesemployed are the same however and from the foregoing description thoseskilled in the art will readily understand how the invention may beapplied to other and more complex systems as well as to other uses inwhich .power at any level is to be delivered through reciprocatingmotion to a load.

A particular embodiment of the present invention has been hereinabovedescribed in considerable detail by way of illustration. It should beunderstood that various other modifications and adaptations thereof maybe made by those skilled in this particular art without departing fromthe spirit and scope of this invention as set forth in the appendedclaims. This application is a division of my copending applicationSerial No. 595,- 535, tiled July 2, 1956.

I claim:

1. An apparatus comprising a nid pressure line; a first reciprocatinghydraulic motor consisting of a cylinder, a piston and an attachedpiston rod; means for supporting said rst hydraulic motor so as topermit the cylinder thereof to oscillate around a pivot; a firstdirection reversing valve and conduits connecting the same -with theopposite ends of the cylinder of said iirst hydraulic motor and withsaid fluid pressure line; a first hydraulic valve actuator for operatingsaid .rst direction reversing valve; a second reciprocating hydraulicmotor consisting of a cylinder, a piston, and an yattached piston rodconnected to the cylinder of the said 'rst hydraulic motor, wherebyoperation of said second hydraulic motor causes the cylinder of saidfirst hydraulic motor to oscillate around said pivot; a second directionreversing valve and conduits connecting the same with the opposite endsof the cylinder of said second hydraulic motor and with said uidpressure line; a second hydraulic valve actuator for operating saidsecond direction reversing valve; a pair of spring-loaded hydrauli-`cally actuated pilot uid control valves connected between said fluidpressure line and said second hydraulic valve actuator; a mechanicallyactivated pilot fluid control valve connected between said liuidpressure line and said rst hydraulic valve actuator, said pilot fluidcontrol valve being actuated directly by said oscillation of thecylinder of said irst hydraulic motor; a first pilot fluid linecommunicating between one end of the cylinder of said rst hydraulicmotor and one of said springloaded hydraulically actuated pilot duidcontrol valves;

12 a second lpilot uid line communicating between 'the other end `of thecylinder `of-'said first hydraulic m'otor and the otherpof saidv'spring-'loaded hydraulically actuated pilot fluid control valves,whereby the pistons 'of 'said 'first and second hydraulic motors eachextend and retract continuously in their respective cylinders in afour-step sequence 'so 'long-as pressure exists in said uid pressureline.

2. An apparatus according to claim 1 wherein said lirst hydrauliccylinder is provided with a shaft and trunnion bearing support to permitits oscillation in a vertical plane.

3. An apparatus according to claim 2 wherein said Amechanically actuatedpilot fluid control valve is a rotary valve in combination with anactuating arm therefor connected at right angles to the trunnion shaft.

4. lAn apparatus according to claim 1 in combination with a backpressure controller connected in the conduit 'between said rst directionreversing valve and the lower end of the cylinder of said rst hydraulicmotor, said pressure controller connected to maintain at least apredetermined minimum pressure below the piston in said cylinder duringthe downstroke to prevent the weight of the piston and piston rodtherein and of the load attached thereto from alone causing thedownstroke of the piston.

5. An apparatus according to claim l in combination with a back pressurecontroller connected in the conduit between said rst direction reversingvalve and the upper end of the cylinder of said rst hydraulic motor,said controller connected to maintain at least a predetermined pressurein the line between said valve and said controller during the-downstroke of the piston in said cylinder, which pressure is sullcientto actuate the spring loaded pilot uid control valves against the springload.

6. An apparatus according to claim 1 in combination with a pressurecontroller connected in the conduit between the iirst directionreversing valve and the upper end of the cylinder of said iirsthydraulic motor, said controller being connected to limit the hydraulicpressure which can be applied above the piston in said cylinder duringthe downstroke thereof.

7. An apparatus according to claim 1 wherein each of said first andsecond pilot fluid lines opens into the cylinder of said rst hydraulicmotor at a point which is covered and sealed by 'the piston of saidmotor in its extreme position.

No references cited.

